The invention relates to a collector-distributor combination for a gaseous and a liquid phase in a column.
Columns filled with a random packed bed or with a structured packing have numerous application possibilities in plants for the petrochemical industry. Frequently, these types of columns are used to separate blends, wherein a gaseous phase is withdrawn via the head of the column and a liquid phase via the base of the column. The random packed beds and the structured packings in the interior of the column are used to improve the interaction between the gaseous and the liquid phase. As a result, for optimal functional capability of the column, the liquid phase as well as the gaseous phase must be distributed uniformly over the entire volume and thus over the entire cross section of the column.
A column according to the prior art has one or more collector and distributor devices, which are distributed over the entire column. In the prior art these types of columns are used mainly on land in so-called on-shore operation. In this type of column according to the prior art, the liquid collector and distributor are designed as a rule as open channels, troughs or bus bars.
Liquid collectors and distributors according to the prior art are distributed over the entire height of the vertically aligned column and installed horizontally. The liquid phase wets the random packed beds or the structured packings, with which the column is filled and flows downward driven by gravity. The gaseous phase moves upwards. Due to the fact that both phases are forced to move through a plurality of narrow channels, the interaction between the two phases is increased. According to the prior art, a liquid collector and distributor is situated between two of these types of packing levels. The liquid drips by virtue of gravity into the collector, is conveyed from there to the distributor and in the distributor is distributed over the entire cross section of the nearest packing level. According to the prior art, these types of distributors are frequently designed as open channels (U profiles) with holes, which distribute over the entire cross section of the column. The intermediate space between the open channels is used for the passage of the gaseous phase. In order to keep the liquid phase out of these passages, the passages in the prior art are frequently covered over. These liquid distributors, which function according to the principle of an open gravity distributor, have been proven in the use of land-based, vertically aligned columns.
The liquid collectors and distributors described in the prior art are not appropriate for use under off-shore conditions like those prevalent on a ship, for example. In off-shore operation, the column is subjected to continuous movement, which takes it out of its vertical orientation. In the most adverse case, an inclined position of several degrees of the column with respect to the vertical can occur over a longer period of time. With this type of use of open gravity distributor systems according to the prior art, it is possible, when the column is in an inclined position, for the liquid not to reach the lowermost point of the collector and distributor system, thereby causing the packing body/packing to be only insufficiently wetted, and thus making it impossible for the column to continue to fulfill its function.
The present invention is therefore based on the objective of designing a collector-distributor combination in such a manner that collecting and distributing the gaseous and the liquid phases is guaranteed even in the case of an inclined position of several degrees of the column.
The present objective is attained in that the distributor for the liquid phase is designed as a pressure distributor for the liquid phase and/or the collector for the liquid phase is designed as a pressure distributor for the gaseous phase.
Because of the inventive design of the distributor as a pressure distributor, distribution is guaranteed independent of gravity and the inclined position of the column. The embodiment as a pressure distributor puts the liquid phase and/or the gaseous phase under pressure in such a way that the respective phase disperses over the entire distributor. As a result, the respective phase gets distributed over the entire cross section of the column. An accumulation of the respective phase in one area of the cross section of the column is avoided. The pressure in the distributor makes sure that the respective phase is distributed against gravity over the entire cross section of the column even when the column is not aligned vertically.
In a preferred embodiment of the collector-distributor combination, the collector for the liquid phase has means, which are suitable for guiding the liquid phase to a central opening, which is connected via an ascending pipe to the distributor for the liquid phase. The ascending pipe expediently has a polygonal, preferably rectangular, or round, preferably oval, particularly preferably circular, cross section, which is suitable in terms of its size to permit gas bubbles to ascend against the flow of the liquid phase. The distributor for the liquid phase is comprised advantageously of at least one distributor pipe connected to the ascending pipe, from which distributor pipe at least one other distributor pipe can branch off, wherein the distributor pipes have any polygonal or round cross section and openings for the liquid phase on the underside.
Above all, inclined flat surfaces are suitable as means for guiding the liquid phase to a central opening in the collector. In this case, the flat surfaces advantageously have an incline that is considerably greater than the expected maximum inclined position of the column. Therefore, even with a maximum inclined position of the column, a residual slope still remains in the collector, through which the liquid phase is conveyed to the central opening. Independent of the inclined position of the column, the liquid phase is guided to the distributor system with the distributor pipes through the ascending pipe connected to the central opening. The dimensioning of the ascending pipe should be selected in such a way that, on the one hand, the possibility exists for gas bubbles within the liquid distribution system to rise through the ascending pipe, and, on the other hand, for a continuous fill level of the liquid phase to be guaranteed in the ascending pipe. Because of the continuous fill level of the liquid phase in the ascending pipe, pressure builds up over the entire distributor system made up of the ascending pipe and distributor pipes, and the pressure guarantees distribution of the liquid phase over the entire length of the closed distributor pipes and thus over the entire cross section of the column. The pressure in the distributor system distributes the liquid phase even against gravity. The distributor pipes of the distributor are expediently distributed uniformly over the entire cross section of the column. The liquid phase exits uniformly on the entire cross section of the nearest packing level through the openings on the underside of the distributor pipes.
Advantageously, the collector for the liquid phase is suitable as a collector and distributor for the gaseous phase. The collector for the liquid phase expediently has at least one chimney for the gaseous phase, wherein the chimney has any polygonal or round cross section and a cap going beyond the cross section of the chimney or a hood going beyond the cross section of the chimney. It is particularly preferred that several chimneys be distributed uniformly over the surface of the collector for the liquid phase.
Because of the preferred embodiment of the collector for the liquid phase as an inclined surface over the entire cross section of the column, the gaseous phase accumulates beneath the collector. The gaseous phase can pass through the collector only via the chimneys distributed over the cross section. The loss in pressure, which the gaseous phase experiences by flowing through the chimneys, makes for uniform distribution of the gaseous phase beneath the next higher packing section. The collector for the liquid phase thus serves advantageously as a pressure distributor for the gaseous phase. Because of advantageously equipping of the chimneys with caps or hoods, which go beyond the cross section of the chimneys, penetration of the liquid phase into the chimneys is prevented and the chimneys are thereby kept open for the gaseous phase.
In another embodiment of the invention, the distributor for the liquid phase is comprised of a flat, closed cylinder with openings for the liquid phase on the underside, wherein the basic surface of the cylinder extends over the entire cross section of the column and the cylinder has at least one chimney passing through it for gas passage. Also in this embodiment of the distributor as a flat, closed cylinder, the distributor functions as a pressure distributor and the liquid phase is distributed over the entire cross section of the column. In order to simultaneously guarantee the permeability of the distributor for the gaseous phase, analogous to the collector, the distributor has one or more chimneys distributed uniformly over the cross section.
In a further embodiment of the invention, the collector for the liquid phase has means, which guide the liquid phase in parts to a central opening, which is connected via an ascending pipe to the distributor for the liquid phase, and to guide the liquid phase in parts to an opening on the outside of the column, through which a specific quantity of liquid can be guided out of the column in a dosed manner. In this embodiment of the invention, the ascending pipe expediently goes beyond the central opening of the collector.
In numerous applications it is necessary to guide liquid out of the column in a defined quantity at various points over the height of the column. In this embodiment of the invention, this is advantageously combined with the collector for the liquid phase. The collector is constructed in such a way that the liquid phase is guided to two points, the central opening and the lateral withdrawal point for the liquid phase. In this case, a bowl-like indentation in the collector is expediently located on the lateral opening of the column. The distribution of the amount of the liquid phase between the central opening and the lateral opening for discharging the liquid phase is regulated in this case by the height by which the ascending pipe goes beyond the central opening of the collector.
In particular, the present invention makes it possible to guarantee uniform distribution of the liquid and gaseous phases in a column over the entire cross section of the column even when there is movement of the column or if it is set up with an inclination with respect to the vertical position.
The invention will be explained in greater detail in the following on the basis of three exemplary embodiments of the collector-distributor combination.